Personally if my lock was just going to be a booster I would go felguard spec. (if the pet kill thing works). Your build was intriguing at first, but probably overkill. A pure affliction lock wouldn't strugge with mana or health regen.

For the felguard spec I would max out mana feed - if your felguard hasn't got mana lifetap and it's got a big chunk again. For solo play I put about 2 points in there 3 would keep it pretty much full. Health funnel him back up to full health if need be (or insta summon a new one).

Does the being out of group and the pet only damaging trick work with just one player? I remember trying an experiment before I heard of this where I was in the group with my low level rogue and would set the pet and of course it didn't help. I'm not sure if i tried the combination where I was out of group and just let the pet kill.

If it does work then you would tag the mob with your lowbee and then pet attack on the felguard. Your lock would do nothing other than maybe fear a mob off if you are struggling or soulstone/healthstone you.